Au/zro < Sub > 2 < / Sub > And Au/x % Ti - Zro < Sub > 2 < / Sub > On The Propylene Epoxidation Reaction

Propylene oxide （PO） is a valuable chemical intermediate. At present, the industrialproduction of PO mainly includes the chlorohydrin process and the halcon process. Thechlorohydrin process produces large amount of chlorine-containing compunds and leads toheavy pollution; while the halcon process relys on the price of the co-products. The directpropylene epoxidation with oxygen or added some clean gas such as hydrogen is a low-costand environmental benign reaction, which attracts much more attention in catalysis field.Currently, research of propylene epoxidation under vapor phase focus on the goldcatalyst with titanium containing supports，however，the catalysts without titanium arementioned only in few patent. This paper focuses on the gold catalyst supported onzirconium for propylene epoxidation. TEM, SEM, XRD, BET and ICP-AES techniques areperformed to characterize the catalysts. The following conclusions have been drawn:（1）A series of0.5%Au/ZrO₂catalysts are prepared by adjusting pH value of the goldprecursor solution, when the catalyst prepared with pH=5of the gold precursor solutionexhibits better catalytic activity than other pH value. With water vapor introduced into thehydrogen and oxygen atmosphere, the conversion of propylene is improved whilemaintaining the selectivity to propylene oxide.（2）Choose0.5%Au（5）/ZrO₂catalyst as the parent, we prepared two series catalysts:x%K-0.5%Au/ZrO₂catalysts and x%Na-0.5%Au/ZrO₂catalysts with different K/Na contentby adding different concentration of KOH and NaOH solution before the reduction of goldcatalyst precursor. We found that the addition of alkali metals not only reduce the optimalreaction temperature, but also improve the selectivity to propylene oxide.The0.4%K-0.5%Au/ZrO₂catalyst exhibits the highest selectivity to propylene oxide，whichcould reach95%。（3）A series of titanium zirconium composites as the supports of gold catalysts areprepared with different titanium content，and with an increase in titanium content, the sizeof composite supports decrease gradually, all about20nm. The gold precursor solution withthe pH=5are applied to prepare a series of Au catalysts for propene epoxidation. Betterselectivity to propylene oxide （higher than90%） at150℃was observed over the catalystswith high content of titanium supports.